Germany's Ultrasone typically scales to the upper echelon headphones. The HFI-2400 headphones are Ultrasone’s flagship consumer model with an official price of $330; while expensive, it's a bargain compared to pro and DJ products that retail for twice as much. No matter the model, Ultrasone’s claim to fame is its S-Logic natural surround sound, which it equates in video parlance to the difference between watching a movie in 2D versus 3D. It all sounds very impressive -- pun intended -- but we'll find out how well it works in our review.Box contents and build quality

The 2400s ship with a black velvet carrying bag, a studio quality nine-foot audio cable, a 6.3mm-to-3.5mm audio adapter, and a packet holding the usual demo CD and documentation. The velvet bag is large and holds the 2400s and the nine-foot cable easily. We really appreciate the cable length, as most headphones typically ship with a four- to six-foot cable; the extra couple of feet can sometimes be useful, especially in a listening room. Ultrasone threads the connector that is inserted into the headphones, while the other side of the cable ends in a 6.3mm studio jack. We really like the threaded connection on the headphone end as it gave a firm connection. All of the plugs were gold plated, including the minijack adapter; there's a debate as to whether this is ever effective, but it can't hurt.

The demo CD that Ultrasone includes is full of mostly classical music by German composers such as Bach and Beethoven; it's useful to test the high range of audio. There are a few other classical tracks on the CD as well as some non-musical audio tracks such as applause and outdoor sounds. The documentation booklet that ships with the 2400s has a decent amount of information in it, but it's very poorly translated. Many of the sentences seem to have been put into a translation program and not edited with regard to syntax or common word usage. We were able to understand everything in the booklet, but it was quite distracting as you spent more time deciphering than learning.

The headphones themselves are built very well. The ear cups can rotate 90 degrees to lay flat to store in the bag. The padding at the top of the headband and around the earphones is soft and very thick. Upon removing the headphone covers, you can find the single 40mm drivers situated behind a protective metal covering. While largely made of plastics, the headphones are given very heavy-duty contruction; there is nothing about the headset that doesn’t ooze quality.

Audio quality and experience

The 2400s are open air headphones, leaving no deliberate sound isolation either inside or outside. People several feet from the headphones can hear them at a volume similar to what a cellphone call would have from the same distance. This also means that sounds from the environment around you will seep in. A preference between open air and closed air headphones is more of a situational issue or matter of personal preference; in terms of this review, the 2400s seemed to let in no more or less outside sounds than we would normally expect.

The S-Logic technology Ultrasone uses in the 2400s is described as putting sound around your ear instead of into it. From our usage, this seems to be an accurate description: athe sound quality felt like that of external speakers, not typical headphones. This effect is accomplished by placing the drivers in the corner of the headphones instead of directly facing into the ear. In our opinion, S-Logic is more than marketing buzz on the package or website; it's a true improvement to the listening experience.

We listened to a variety of tracks ranging from the classical tunes provided by Ultrasone to techno, dance, rock, and pop. We were consistently satisfied with the audio quality of the 2400s given their price point. We even compared the 2400s side by side to the Beats by Dre that we recently reviewed. The audio quality was quite comparable between the two, but the comfort of the larger 2400s and their open air design was our personal preference. The 40mm drivers provided ample volume and could handle highs, mids, and lows from a variety of musical styles adeptly, without being drowned out or overemphasized.

Wrapping up

If you’re in the market for a very high quality pair of headphones with excellent acoustics, you need to at least consider the 2400s. The combination of great build quality and excellent sound should put these on the short list of anyone who is shopping for a pair of open air headphones in the $300 to $400 price range. It's a cliche, we know, but this pair was music to our ears.